In turbomachinery and in many other mechanical applications, it is often required that fluid or air in a high pressure cavity be prevented from flowing into a lower pressure cavity. Various types of seals have been introduced for such a purpose. One type of seal utilizes the differential pressure between cavities to assist in seal seating. A loss of pressure may cause such seals to lose their effectiveness. This is particularly true in rotating machinery where centrifugal forces may cause the seal to bind if a sufficient pressure force is not present to provide proper seating of the seal. Thus, a need is seen for a differential pressure sealing means which is effective as a seal between rotating members even during times when the pressure force which enables proper sealing is reduced.
Typically, a piston ring having a diagonal split and generally referred to as a split ring is used for sealing in current state of the art differential pressure rotating seal applications when a sufficiently high pressure exists. The split allows the ring to grow radially under centrifugal forces. The piston ring seats on a low pressure side of its retention groove and an adequate seal is established. However, high centrifugal forces on the ring may cause the piston ring to bind against a radially outer rotating member and not seat due to the frictional force. A leakage path may therefore be formed around the piston ring.
The prior art schematic illustration of FIG. 1 shows a portion of a gas turbine engine having a split ring seal 2 situated between a rotating annular seal member 4 and core rotor 6. Both the seal member 4 and core rotor 6 rotate about an axis of rotation (not shown) of the engine. The split ring seal 2 (or piston ring) is situated to prevent high pressure air P.sub.2 from leaking into the area of low pressure air P.sub.1 and serves to mitigate the leakage of high pressure air in low pressure flowpath 8.